Effect of ionic liquid [emim][OAc] on the set recovery behavior of densified wood

Abstract

Wood modification techniques, like densification, can improve the mechanical performance of low-density and undervalued wood species, rendering them suitable for high-value engineering applications. Nevertheless, densified wood (DW) commonly manifests a set recovery (SR) phenomenon when exposed to water, negating the enhancements achieved through densification. Our method addresses the SR issue and the non-recyclability associated with conventionally produced DW using chemical techniques in wood densification. To mitigate SR in DW, an ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate was impregnated as a cellulose plasticizing agent prior to wood densification. This method facilitated permanent deformation within the cellulose network, resulting in negligible SR. Moreover, the DW treated with IL (DW_1w) demonstrated an increase in both modulus of rupture and modulus of elasticity after water washing and subsequent redrying, in comparison to the untreated control (UC). Notably, spectroscopic (FTIR) analyses indicated that the chemical structure of DW_1w remained akin to that of UC. Additionally, the IL leached out during the DW-water washing step can be recovered. This research contributes to advancing sustainable alternatives to less ecologically friendly (chemical) pretreatment methods to reduce SR related issues in DW.